Non-Volatile Memory (NVM) is used extensively in solid-state storage devices (SSDs), also referred to as solid-state drives. Currently, NAND Flash is the most common type of NVM used in SSDs.
Originally, NAND flash employed charge trapping to store one bit per cell. This was referred to as Single Level Cell (SLC) NAND. As the technology matured and as the market demanded lower cost per bit, new NAND Flash emerged that can store two bits per cell (multi-level cell or MLC) and even three bits per cell (triple-level cell or TLC). SLC, MLC, MLC with improved endurance (MLC+) and TLC are referred to herein as NVM storage modes. Research is also pushing development of four bit per cell (quad-level cell or QLC) NAND.
Consumers of SSDs are often looking for a range of properties in their drives. For example, some customers are looking for read-intensive drives and the lowest price per GB of storage. Other customers want a more write-intensive drive and are willing to pay more per gigabyte (GB) in order to obtain that performance. As such, it becomes necessary for SSD manufacturers to produce a number of distinct SSD products, also referred to in relation to stock keeping units (SKUs). These different SSD SKUs are physically different devices and often contain different types of NAND. Managing SKUs and procuring NAND is a major challenge for an SSD vendor.
Improvements in the use of NVM in SSDs are desirable.